1. Field of the Invention
The present invention relates generally to filters of the type having a fluid permeable filtering element which is saturated with oil to entrap airborne contaminants. More particularly, the invention sets forth a wet filter construction and related method for initially preparing the filtering element and subsequently cleaning the same in preparation for subsequent usage.
2. Description of the Prior Art
Filters for filtering air employing petroleum based oil saturated filtering elements are known in the prior art. Typical applications include small appliances employing single cylinder internal combustion engines, and off-road vehicles which are likely to encounter great volumes of airborne dust. The latter must frequently have the air filter cleaned or renewed. Filters employing reusable, oil saturated filtering elements have come into favor since preparing the filtering element for reuse is a relatively easy operation.
These filters typically employ elements comprising open cell synthetic resin foams or woven fabric materials. The filtering element is saturated with oil prior to being installed in the filter housing. Oil provides a surface which readily entraps small airborne solids. When the filtering capacity is reached, the filtering element must be cleaned, and then may be reoiled and reinstalled in the filter housing. U.S. Pat. No. 2,961,710, issued to Norman H. Stark on Nov. 29, 1960, shows a method for making an open cell synthetic resin foam filtering element.
Due to environmental concerns, traditional cleaning of a used filtering element requires modification. Conventional practice, particularly among homeowners and laymen not having professional facilities for cleaning, has been to squeeze or wring as much oil as is readily feasible from the filtering element, then to wash the filter in a solvent or with water and soap.
Washing the filter in a solvent, such as gasoline or kerosene entails health and environmental hazards. Hydrocarbons are known carcinogens, and otherwise interfere with health of the user and with the ecology if discharged directly into the ground and ground waters. Washing the filter in water with a detergent or soap creates, if not equivalent health and environmental problems, practical problems. For example, petroleum based oil resist being dissolved by water and soap, and residual undissolved oil may coat or foul domesting plumbing systems and septic tanks. Soaps and detergents may possibly leave objectionable residues in sinks and plumbing systems. Soap and detergents may not be fully effective in cleaning the filtering element, or may require undue consumption of the soap and detergent to achieve satisfactory results.
It is therefore desirable to employ an oil which is readily disposed when cleaning the filtering element. The prior art has proposed biodegradable oils to mitigate the problem of fouling and incomplete dissolution. U.S. Pat. No. 2,019,241, issued to Howard F. Weiss on Oct. 29, 1935, and 2,403,261, issued to Llewellynn J. Clark on Jul. 2, 1946, illustrate air filters impregnated with vegetable oils.
There remains a need for a method of cleaning filters impregnated with oils in a manner enabling ready and complete cleaning of the filters, and assuring minimal fouling of waste disposal facilities.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.